The present invention relates to a method and apparatus for actuating a reversible vehicle occupant protection device in a vehicle having a sensor system which senses driving state data, and a reversible vehicle occupant protection device which can be triggered (and thus moved into an operative position) before a collision occurs. In such systems, a control signal for triggering the vehicle occupant protection device is activated if a critical driving state or a critical driving situation is present, and is deactivated if the critical state of the vehicle ends.
A critical driving situation or driving state is understood to mean, for example, an emergency braking operation or oversteering or understeering of the vehicle, for example skidding of the vehicle. In such critical situations, preventative measures for protecting vehicle occupants are activated and deactivated again when the danger has passed. The information for identifying a critical situation and for initiating preventative measures is supplied by sensors such as, for example, those which are included in a braking assistant or of a vehicle movement dynamics control system. Such systems can perform early detection of critical driving situations such as skidding or emergency braking of the vehicle, and can generate or set a control signal, such as a software flag or a status bit, preventatively pretensioning a reversible seat belt pretensioner.
German patent document DE 101 21 386 C1, for example, discloses a method for actuating a reversible vehicle occupant protection means in a motor vehicle having a driving state sensor system which senses driving state data, and a reversible vehicle occupant protection means that can be triggered, and thus moved into an operative position before a collision occurs. The driving state data are monitored for a state of “emergency braking”, and if a state of “emergency braking” is detected the vehicle occupant protection means is actuated. The data processing device also detects a state of “oversteering” and a state of “understeering”. If such a state of “emergency braking” and/or the state of “oversteering” and/or the state of “understeering” is present, the reversible vehicle occupant protection means is actuated. After the critical driving state has ended, the actuated vehicle occupant protection system is deactivated.
As the safety requirements in vehicles increase, and given the increasing number of controllable and reversible vehicle occupant protection devices as preventative measure in a critical driving situation, a differentiated evaluation of the driving state or of the driving behavior is necessary.
Even if the control signal for actuating the reversible seat belt pretensioner is set only briefly when a critical driving situation is identified, the seat belt pretensioner remains tensioned until an associated release signal is set if the vehicle movement dynamics and physical and mechanical release conditions for the release of the seat belt pretensioner are met. A control signal for actuating the reversible seat belt pretensioner which is set only briefly is unsuitable for actuating further vehicle occupant protection devices (for example a seat which is dynamic in terms of vehicle movement), since the latter requires persistent actuation which lasts until a resetting condition has been met.
One object of the invention, therefore, is to provide an improved method and an apparatus of the type mentioned above which achieves reliable and precise control of the vehicle occupant protection means is made possible.
This and other objects and advantages are achieved by the method according to the invention, in which a reversible vehicle occupant protection device that which can be activated by a control signal, and thus moved into an operative position, before a collision occurs is deactivated only if the critical driving state ends, and also as a function of at least one further condition which represents at least one sensed, in particular controllable driving behavior or a driving state.
The advantage of this method is that the control signal is suitable for a plurality of controllable vehicle occupant protection systems, as a triggering signal which takes into account essentially all the possible critical driving situations (for example skidding, rolling over or emergency braking of the vehicle), and permits a differentiated actuation of a plurality of different vehicle occupant protection devices (for example, a seat belt pretensioner and/or a seat which is dynamic in terms of vehicle movement). The triggering control signal is set until a controllable driving behavior; in particular its preventative measure is activated by active closed-loop or open-loop control of a vehicle system. This provides improved vehicle occupant protection. Furthermore, the driver perceives the differentiated actuation of the various vehicle occupant protection devices which takes into account various driving situations, and is thus improved as being plausible.
In one preferred embodiment, a vehicle movement dynamics control system is monitored as a function of time and/or state for a further driving behavior which is to be sensed. In particular, the vehicle movement dynamics control system is monitored for nonactivation. In this context it is checked whether the vehicle movement dynamics control system is deactivated for a predefined time period of at least 1 sec. In other words, it is checked whether no intervention of the vehicle movement dynamics control system occurs for a time period of, for example, at least 1 sec. If so, an uncritical driving situation or an uncritical and thus controllable driving behavior is detected, and the control signal can thus be reset (deactivated) for preventative triggering of one or more vehicle occupant protection systems.
In order to detect a critical driving situation or a critical driving behavior, various vehicle movement dynamics control systems, such as a brake control system, particularly an antilock brake system, referred to as ABS, an electronic braking force distribution system (referred to as BFDM), an electronic stabilization program (referred to as ESP), or a traction controller (referred to as TC), are expediently monitored for deactivation and/or activation. In addition, in order to reset the control signal, a check is made whether there has been no intervention in one of these systems for at least 1 sec. This permits sufficiently good detection of a resumption of a controllable driving behavior or driving state, and of the sensation of risk of a vehicle user by derivation therefrom.
As a further condition, advantageously the yaw rate may be monitored for undershooting of a predefined first threshold value for a time period of at least 1 sec, in which case an uncritical driving state or an uncritical driving behavior is detected, and the control signal is deactivated. The first threshold value can be selected as a function of the vehicle speed, and for example decreased at high speeds. This facilitates resetting at high speeds, because it has been found empirically that drivers drive with a greater degree of attention at relatively high speeds.
Additionally or alternatively, it is possible in a further case to check as a further condition whether the wheels of the vehicle are stationary and a predefined second threshold value of the yaw rate continues to be undershot. For skidding or rotating of the vehicle when the wheels are stationary, the yaw rate is therefore also monitored as an evaluation variable. However, selecting different threshold values permits separate adaptation to the particular situation that the vehicle is rotating about the vertical axis while the wheels are stationary, which can occur when the underlying surface is slippery.
The undershooting of a threshold value is preferably monitored for a predefined time period, particularly for a time period of at least 1 sec. If the predefined threshold value is undershot for at least 1 sec, an uncritical driving situation is identified and the control signal is reset. If, on the other hand, the threshold value of the yaw rate is exceeded, rotation or skidding of the vehicle is identified.
As a further condition for resetting the control signal, it is possible to check whether no partial braking operation which is triggered by a driver and no autonomous partial braking operation (for example of a braking assistance system), is occurring. Autonomous partial braking operation is understood to be in particular an emergency braking operation which is triggered automatically in response to sensing of the surroundings. When a partial brake operation or emergency braking is triggered by a driver, it is concluded that a hazardous situation or emergency situation is present due to the driver's behavior. For this purpose, at least one parameter, such as the braking pressure, the speed of the activation of the brake pedal and the speed with which the acceleration pedal is released, is used to evaluate the braking process. If no partial braking operation is triggered by a driver and no autonomous partial braking operation occurs for a time period of at least 1 sec, an uncritical driving state is identified and the control signal is deactivated or reset.
By means of the acquired driving state data of one of the vehicle movement dynamics control systems or a sensor system and its monitoring for downward and/or upward transgression of threshold values it is possible to identify oversteering, understeering and/or emergency braking of the vehicle as critical driving states. For example, for this purpose changes in the steering angle, the speed of the vehicle, the wheel speed, the yaw rate, the lateral acceleration, the longitudinal acceleration, a resulting overall acceleration or an actual coefficient of friction are sensed and monitored for upward transgression and/or downward transgression of threshold values, in particular for a predefined time period.
If a critical driving situation occurs, it is possible, by means of the actuated control signal, to activate at least one reversible vehicle occupant protection system as a preventative measure for protecting the vehicle occupants. A reversible vehicle occupant protection means is one whose purpose is to reduce the stressing of a vehicle occupant in the case of a collision. In this context, the protection system can be changed repeatedly from the initial state to an operative state, and reset from the operative state back to the initial state. For example an electric seat adjustment device, a reversible seat belt pretensioner, an electric adjustment device for vehicle openings and/or an electrically adjustable impact protection device are activated as reversible vehicle occupant protection systems.
The device according to the invention has a control unit which can activate a control signal for triggering at least one vehicle occupant protection system if at least one critical driving state is present, and can be deactivated if the respective critical driving state ends and as a function of at least one further condition which represents at least one sensed driving behavior. The control unit continuously checks whether one of the critical driving states of oversteering, understeering or emergency braking is present. If so, one or more reversible vehicle occupant protection systems is activated. In particular, the activation of the vehicle occupant protection systems when more than one of the critical states of emergency braking, understeering and oversteering are present simultaneously, is adapted to a combined hazard. In order to deactivate the vehicle occupant protection system by resetting the triggered and set control signal, in addition to the ending of the identified critical driving situation, at least one further condition that is indicative of a controllable driving behavior of the vehicle, is used.
In one particular embodiment, the control unit outputs a control signal which corresponds to an identified state. The control signal, and the information which is associated with it about the states of “oversteering”, “understeering” or “emergency braking”, are also made available to other vehicle devices, for example for performing open-loop and/or closed-loop control over other operating functions of the vehicle.
The device preferably has a databus and the control unit transmits the control signal onto the databus. The control signal and the information about the states of “oversteering”, “understeering” or “emergency braking” can thus be called via a uniform interface.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
Parts which corresponds to one another are provided with the same reference symbols in all the figures.